Micro channel devices include, but are not limited to, devices which carry one or more samples for processing and/or analysis by a sample processing apparatus. Such devices have included, for each sample, at least one processing channel and one or more processing agent chambers, etc. One approach for moving a processing agent from an agent chamber to a processing channel has included using pressurized air. A DNA sequencer is a sample processing apparatus that can determine an order of the nucleotide bases (adenine, guanine, cytosine, and thymine) in a DNA sample. Generally, the sample is carried by a micro channel device such as a biochip, a lab-on-a-chip, or the like. The DNA sample is controllably moved through the processing channel where it is processed. Reagents, wash solutions, primers, dyes, and/or other agents have been moved from the agent chambers to the processing channel to facilitate processing the sample via pressurized air.
By way of example, with one DNA sequencer a bucchal swab with a bio-sample is processed to extract one or more DNA strands. An extraction fluid such as a lyses reagent is moved, via pressurized air, from an agent chamber to the channel for the extraction. The DNA strand is then moved to a purification region of the micro channel device where a purification fluid, such as a wash solution, is moved, via pressurized air, from an agent chamber to the channel for purification. The DNA strand is then moved to a replication (thermocycling amplification) region where the DNA strand is replicated and labeled via polymerase chain reaction (PCR). Replication and labeling fluids such as a primer and fluorescent dyes are moved, via pressurized air, from agent chambers to the channel for replication and labeling. The processed DNA strand is then moved to a separation and analysis region where the nucleotides are separated via electrophoresis and analyzed via an optical detection system.
Generally, each agent chamber has an entrance and exit that are initially closed with thin plastic material covers, which can be opened by exposing the covers to the pressurized air. However, achieving uniform material thickness and burst strength of the covers for corresponding chambers across channels is difficult, and the covers are expected to burst under a fairly wide range of pressures. This can be problematic since in a multi-channel chip it is not practical to break a large number of covers at the same time with individually controlled air supply lines. Another approach uses a common air supply line. However, the agents in the chambers in which the covers have been opened at a lower pressure must be prevented from moving while the pressure rises higher to burst open the covers of other chambers until all of the covers have been opened. Unfortunately, this may introduce a risk of premature release of fluid into process for some samples before others, causing non-uniformity in the process. Generally, the covers should be weak enough to be readily broken with reasonable levels of air pressure, but strong enough to sustain vibration and shock during shipping and handling. These conflicting requirements may put potentially costly constraints on the covers.